demilitarized zoneSign indicating the military demarcation line in the woods near P'anmunjŏm, in the demilitarized zone (DMZ) separating North and South Korea.Tech. Sgt. Scott Stewart/U.S. Department of Defense

The demilitarized zone (DMZ) incorporates territory on both sides of the cease-fire line as it existed at the end of the Korean War (1950–53) and was created by pulling back the respective forces 1.2 miles (2 km) along each side of the line. It runs for about 150 miles (240 km) across the peninsula, from the mouth of the Han River on the west coast to a little south of the North Korean town of Kosŏng on the east coast. Located within the DMZ is the “truce village” of P’anmunjŏm, about 5 miles (8 km) east of Kaesŏng, North Korea. It was the site of peace discussions during the Korean War and has since been the location of various conferences over issues involving North and South Korea, their allies, and the United Nations.

The areas north and south of the DMZ are heavily fortified, and both sides maintain large contingents of troops there. Over the years there have been occasional incidents and skirmishes, some of them quite serious. U.S. Pres. Lyndon B. Johnson was visiting Seoul in November 1966 when North Korean infiltrators ambushed an American patrol less than a half-mile (800 metres) south of the DMZ. This incident sparked a low-intensity conflict that claimed the lives of hundreds of Koreans and dozens of Americans over the next three years. Small arms and artillery fire became commonplace along the 38th parallel, and in 1967 U.S. commander Maj. Gen. Charles H. Bonesteel III asked the Pentagon to reclassify the area between the Imjin River and the DMZ as a hostile fire zone for the purposes of combat pay and decorations. The conflict reached its peak in January 1968, when a 31-man North Korean commando team crossed the DMZ and attempted to assassinate South Korean Pres. Park Chung-Hee. Days later, North Korean patrol boats captured the USS Pueblo, a U.S. Navyintelligence ship, and its 83 crewmen (one crew member died of wounds sustained in the initial attack on the ship, and the surviving crewmen were not released until December 1968). The United States and South Korea responded by dramatically increasing counterguerrilla patrols along the DMZ; aided by a $100 million security assistance grant from the United States, South Korea completed an anti-infiltration fence that ran the length of the DMZ.

military policeRepublic of Korea Military Police officer in the Korean Demilitarized Zone (DMZ), P'anmunjŏm.Johne A. Lee, U.S. Marine Corps/Department of Defense

Tensions rose again in August 1976, when a routine tree-pruning operation brought the peninsula close to open war. For several months out of the year, a poplar tree obstructed the view between a UN observation post in the P’anmunjŏm Joint Security Area and a UN guard house known as Checkpoint 3 (CP 3) at the Bridge of No Return. CP 3 was a very short distance from the military demarcation line separating the North from the South, and it was not uncommon for North Korean soldiers to attempt to kidnap UN and South Korean troops who were posted there. For this reason, regular trimming of the poplar tree near CP 3 was a vital matter of security for UN forces. On August 18, 1976, two U.S. Army officers, a South Korean officer, a squad of enlisted men, and a crew of South Korean auxiliaries were dispatched to trim the tree. North Korean authorities in the jointly administered area had been made aware of the operation ahead of time and had registered no objections. When the tree-trimming crew and its military escort arrived, North Korean troops initially did nothing but watch. Suddenly, a North Korean officer ordered the operation to halt and called for reinforcements. Ignoring the order, the crew continued working. Then, without warning, the North Korean officer ordered his men to attack. Seizing axes from the work crew, North Korean soldiers murdered the two American officers and severely wounded many of the UN troops. Days later, in an overwhelming show of force, the U.S. and South Korea launched Operation Paul Bunyan to complete the trimming of the tree. This time the mission was carried out by more than 300 troops, accompanied by overflights of B-52 bombers, fighter aircraft, and dozens of attack helicopters. A stump was all that remained of the poplar tree, although this was eventually cleared for a memorial to Arthur Bonifas and Mark Barrett, the two American officers who had been killed.

P'anmunjŏm: Bridge of No ReturnCheckpoint 3 at the Bridge of No Return, P'anmunjŏm, central Korea. A memorial to two U.S. officers killed in the so-called “tree-trimming murders” of August 18, 1976, was erected where the poplar tree at the centre of that incident once stood (lower left).Filzstift

It was long assumed by Western analysts that provocations such as these had been conducted with the approval or at least tacit acknowledgment of the Soviet Union. Documents released after the collapse of the U.S.S.R., however, indicated that, in the wake of Soviet Premier Nikita Khrushchev’s de-Stalinization program, North Korean leader Kim Il-Sung had been largely acting without Soviet support. This could explain why, in the wake of the P’anmunjŏm axe murders, Kim took the unusual step of issuing an official statement of regret for the deaths of the Americans. As a result of the international backlash from communist and nonaligned nations typically sympathetic to North Korea, violent incidents along the DMZ dropped sharply over the subsequent decades.

Once farmland and subsequently a devastated battleground, the DMZ has lain almost untouched since the end of hostilities and has reverted to nature to a large extent, making it one of the most pristine undeveloped areas in Asia. The zone contains many ecosystems including forests, estuaries, and wetlands frequented by migratory birds. It serves as a sanctuary for hundreds of bird species, among them the endangered white-naped and red-crowned cranes, and is home to dozens of fish species and Asiatic black bears, lynxes, and other mammals. Barring a resumption of hostilities, perhaps the greatest threat to the wildlife in the DMZ is the presence there of more than one million land mines and other unexploded ordnance.

In mid-2007 limited freight-train service was resumed across the zone, but it was suspended a year later after a South Korean tourist was shot and killed by North Korean border guards.